The history of the idea of conservation laws; whether the discovery of conservation laws was fueled by PSR-like philosophical-like concerns (e.g. Leibniz?), by lower level intuitive concerns, or other means.
If I'm not mistaken, Maslama al-Majriti beat Antoine-Laurent de Lavoisier to the punch on the principle of the conservation of mass by about 8 centuries. As far as I can tell, he was closer to the practical side (like refining metals and creating medicines, not like proving theorems or arguing from first principles) of the theoretical-practical continuum (or, if you prefer, the philosopher-craftsmen continuum) than Leibniz.
What is your source for the claim? Google finds many people making the claim, but I'm not convinced that Maslama made it. I think he did one burn where the amount lost as gas was about the same as the amount of oxygen gained, within the error of his not very accurate scale. If he drew philosophical conclusions from this, I would count it against him, but I don't think he did.
One of the sharpest and most important tools in the LessWrong cognitive toolkit is the idea of going meta, also called seeking whence or jumping out of the system, all terms crafted by Douglas Hofstadter. Though popularized by Hofstadter and repeatedly emphasized by Eliezer in posts like "Lost Purposes" and "Taboo Your Words", Wikipedia indicates that similar ideas have been around in philosophy since at least Anaximander in the form of the Principle of Sufficient Reason (PSR). I think it'd be only appropriate to seek whence this idea of seeking whence, taking a history of ideas perspective. I'd also like analyses of where the theme shows up and why it's appealing and so on, since again it seems pretty important to LessWrong epistemology. Topics that I'd like to see discussed are: